1. Field of the Invention
The present invention is concerned with disposable cartons for packaging such merchandise as eggs and characteristically comprises a bottom tray portion formed to provide cells for the packaged goods, a top cover portion hinged to the rear of the tray and a latching flap hinged to the front of the tray. The latching flap is adapted to coact with the cover for retention of the closure. More particularly the invention concerns a novel structure on the latching flap which provides a positive restraint for the cover so that when crushing forces are applied, generally perpendicular to the plane of the cover, cover support ribs are so positioned on the flap to prevent the cover member from coming into crushing contact with the carton contents.
2. Description of the Prior Art
Egg cartons of this general type have been common for many years. An early type is shown by Cox U.S. Pat. No. 2,517,465 in which the latching flap is exterior of the cover and provided with tabs insertable into slots in the front face of the cover. Cartons of the same general nature but having an inner latching element are shown by Schilling U.S. Pat. No. 2,600,130 in which the latching flap is extended to provide upper cells intended to afford greater protection to the packaged eggs. Schilling provides a friction type latch in which a protrusion in front of the flap engages a matching recess in the cover.
Many attempts have been made to improve on the Schilling carton by different specific configuration of latching mechanisms. Most of the subsequent development has eliminated the extension of the latching flap as an unnecessary precautionary structure, it being found that eggs supported in properly designed cells of the tray suffer little breakage during transit under any reasonable handling without the positive cell structure in an upper part of the carton.
For the most part, egg cartons are today filled and closed on automatic machinery which imposes certain restrictions on acceptable structures. A further restraint on acceptable structures is imposed by the characteristics of the material from which the carton is formed. Most such cartons are prepared on molding machinery from either wood pulp or thermoplastic material and the structure must be such that it can be formed from these inexpensive materials at high speed and readily stripped from the molds. Each of the two types of material (pulp and thermoplastic) and the types of equipment on which these may be formed has its own idiosyncrasies to which the carton structure must accommodate.
Much of the effort toward design of molded egg cartons has been concerned with adaption to molding machines, materials and techniques and to the demands of automatic filling and closing machinery. U.S. Pat. No. 3,648,916 discloses egg carton structures together with their associated locking mechanism which are similar in construction to the egg carton structures of the present invention. The carton structures in this patent resist crushing compressive forces by virtue of a recess molded in the central portion of the carton cover which presses against a cross rib member in the cellular bottom section when compression is applied to the carton cover section.
Absent such a recess in the central portion of the cover which provides a protrusion to bear against one of the cross ribs cellular sections, there is a pronounced tendency when compressive forces are applied to the cover, for the front wall of the cover to roll down below its intended position whereby the upper edge of the aperture, forming the cover latching portion, slides over and down the upper portion of the latching flap element. Obviously when forces are exerted against the cover in a direction generally perpendicular to the plane of the cover and this rolling action occurs it will cause damage to the fragile contents of such cartons, i.e. eggs and the like.